LCDs are commonly used as display devices for compact electronic apparatuses, because they not only provide good quality images with little power consumption but also are very thin. A typical LCD includes a liquid crystal panel, a backlight module, and a driving circuit. The backlight module is positioned adjacent to the liquid crystal panel, and is configured to provide uniform light beams to the liquid crystal panel. The driving circuit is configured to drive the liquid crystal panel.
Referring to FIG. 5, a typical driving circuit 2 of an LCD is shown. The driving circuit 2 includes a control circuit 20, a common voltage generator 21, a gate driving circuit 22, a data driving circuit 23, and a pixel control circuit 24. The pixel control circuit 24, the gate driving circuit 22 and the data driving circuit 23 are located on one of two substrates (not shown) of the LCD. The common voltage generator 21 and the control circuit 20 are mounted on a printed circuit board (not shown). The control circuit 20 provides RGB data voltage signals to the data driving circuit 23. The control circuit 20 also provides operation voltage signals, such as gate-on voltage signals and gate-off voltage signals, to the gate driving circuit 22. The data driving circuit 23 and the gate driving circuit 22 respectively transmit the RGB data voltage signals and the operation voltage signals to the pixel control circuit 24 according to a predetermined timing control regime. The common voltage generator 21 is configured to output corresponding standard common voltages to the pixel control circuit 24, when the LCD 2 displays different gray images. The corresponding standard common voltages are written to the common voltage generator 21 by a one-time programmable (OTP) burning process before the LCD 2 is used for the first time.
The pixel control circuit 24 includes a number x (where x is a natural number) of gate lines 241 that are parallel to each other and that each extend along a first direction, and a number y (where y is also a natural number) of data lines 242 that are parallel to each other and that each extend along a second direction orthogonal to the first direction, a plurality of thin film transistors (TFTs) 261 that function as switching elements, a plurality of pixel electrodes 262 and a plurality of common electrodes 263. The plurality of gate lines 241 and the plurality of data lines 242 cross each other, thereby defining a plurality of pixel units (not labeled) of the pixel control circuit 24. Each of the TFTs 261 is provided in the vicinity of a respective point of intersection of the gate lines 241 and the data lines 242, and includes a gate electrode 2611, a source electrode 2613 and a drain electrode 2615. The gate electrode 2611, the source electrode 2613 and the drain electrode 2615 are connected to a corresponding gate line 241, a corresponding data line 242 and a corresponding pixel electrode 262 respectively.
The control circuit 20 transmits corresponding signals to the gate driving circuit 22 and the data driving circuit 23 so that the gate driving circuit 22 and the data driving circuit 23 start working. The gate driving circuit 22 outputs scanning voltage signals Vg to the gate electrodes 2611 of the corresponding TFTs 261 via the gate lines 241 in order to switch on or switch off the TFTs 261. At the same time, the data driving circuit 23 outputs data voltage signals Vs to the source electrodes 2613 of the corresponding TFTs 261 via the corresponding data lines 242. If the TFTs 261 are switched on, the data voltage signals Vs are transmitted to the corresponding pixel electrodes 262 via the data lines 242, source electrodes 2613, and drain electrodes 2615. The common voltage generator 21 outputs the standard common voltage to all the common electrodes 263. Thus, an electric field generated between each activated pixel electrode 262 and the common electrode 263 is applied to liquid crystal molecules (not shown) of the LCD.
Commonly, when the LCD displays a gray scale image using an inversion driving method, potential differences between the pixel electrodes 262 and the common electrodes 263 facing toward the corresponding pixel electrodes 262 in adjacent time frames are required to maintain a constant value. The constant value is equal to an absolute value of a voltage difference between the data voltage signal Vs and the standard common voltage. However, parasitic capacitance may be generated between two electrodes of each TFT 261. In this situation, a voltage signal transmitted to the pixel electrode 262 is interfered with by the parasitic capacitance and deviates from the corresponding data voltage signal Vs. Thus the potential differences in adjacent time frames cannot maintain the constant value, and the resulting images displayed by the LCD are defective. In particular, the images are liable to flicker. Furthermore, the parasitic capacitance can be exacerbated by high ambient temperatures, and when the LCD is continuously used for an extended period of time. In these situations, the flickering of the images may be considerable.
What is needed, therefore, is a driving circuit and a driving method of an LCD that can overcome the above-described deficiencies. What is also needed is an LCD using such a driving circuit.